1. Field of the Invention
The present invention relates to an imaging apparatus.
2. Description of the Related Art
In a video camera or digital camera that has a zoom lens system, the focal length is changed to the telephoto side or wide-angle side, while the focus position is kept constant, by moving the zoom lens so as to change the zoom ratio, thereby changing the object distance. As a technique for complementing for an optical zoom, an electronic changing-magnification system (electronic zoom) is widely used. Using an electronic zoom can obtain the great advantage of achieving a reduction in size as compared with an imaging apparatus designed to realize wide-range magnification conversion using an optical system alone, although causing a considerable deterioration in image quality relative to an optical zoom.
Jpn. Pat. Appln. KOKAI Publication No. 6-339083 discloses a technique of matching the magnification of a bifocal optical system to that of an optical finder by changing-magnification processing using an electronic zoom. Jpn. Pat. Appln. KOKAI Publication No. 2003-283910 discloses a technique of sharing a driving control system between an optical finder and the imaging lens of a step zoom and selecting a step zoom with a magnification that does not exceed the magnification of the optical finder and is nearest to it so as to almost match the field angle of the optical finder to that of the imaging system, thereby adjusting the field angle using an electronic zoom. Jpn. Pat. Appln. KOKAI Publication No. 2001-136436 discloses a technique of performing changing-magnification processing by using an optical/electronic changing-magnification technique for canceling a variation in field angle with a change in imaging mode (for still images/moving images).
As a technique unique to an electronic zoom function, enlargement interpolation processing is mainstream, which changes the focal length to the telephoto side without moving the zoom lens by converting an obtained image with a pixel count smaller than that of the output of an electronic imaging device into a video signal corresponding to the pixel count of the output. A video camera having such an electronic zoom function cannot obtain an image with a size larger than the light-receiving screen size of the electronic imaging device, and hence cannot be zoomed to the wide-angle side, although can be zoomed to the telephoto side. In contrast to this, there have been provided apparatuses and methods that generate images substantially on the wide-angle side by using the difference between the pixel count of an electronic imaging device and the pixel count of an output image while the lens is fixed.
As an imaging apparatus that can perform such electronic zooming, for example, Jpn. Pat. Appln. KOKAI Publication No. 2000-295530 discloses a solid-state imaging apparatus that has a two-dimensional array of photoelectric conversion pixels and randomly accesses the photoelectric conversion pixels. This solid-state imaging apparatus comprises a first skip means for reading out arbitrarily designated pixels and a second skip means for reading out an image area smaller than the image area read out by the first skip means, and matches the number of pixels read out by the first skip means to that by the second skip means.
In addition, Jpn. Pat. Appln. KOKAI Publication No. 10-42183 discloses an imaging apparatus that comprises a first adjusting means for optically changing the field angle of an image, a second adjusting means for electronically changing the field angle of an image, and a control means for determining a field angle by controlling the first and second adjusting means, wherein the control means causes the second adjusting means to adjust the field angle to a field angle desired by a user, and substantially shifts the control of the field angle from the second adjusting means to the first adjusting means while holding the field angle. More specifically, this imaging apparatus uses a CCD type electronic imaging device. When electronic zooming is performed, the apparatus reads out all pixels from the CCD type electronic imaging device and temporarily stores them in a frame memory or the like. The apparatus then performs electrical interpolation processing on the basis of a pixel signal associated with the small number of pixels included in a partial area of the entire field angle, thereby generating an output image with a desired field angle.
Furthermore, Jpn. Pat. Appln. KOKAI Publication No. 2002-314868 discloses an imaging apparatus that controls an electronic zoom means for performing electronic zooming that changes an imaging position and a cutout field angle as a cutout range of imaging field angles in combination with an optical zoom by using an electronic imaging device that can designate a readout position and range on the electronic imaging device by performing thinning-out read operation of a photoelectric conversion signal on the electronic imaging device with the same clock-count as that for readout operation by the X-Y address scheme, thereby making the zoom range of an output field angle associated with an image signal to be finally output wider than either of an optical zoom range that can be obtained by only changing the imaging field angle and an electronic zoom range that can be obtained by changing only the cutout field angle.